1. Field of the Invention
The present invention generally relates to a lightweight, stringerless surfboard with channels that provide superior flexibility characteristic and rigidity while the surfboard is moving on a wave.
2. Description of Prior Art and Related Information
The material bending of a surfboard in the water, also commonly termed “flex,” is one of the most important aspects of a modern surfboard. Flex allows the foam material of the surfboard to bend without breaking, store potential energy, return the surfboard to its original shape, release the stored potential energy and turn it into kinetic energy. The principle of flex can be understood by understanding how a surfboard behaves as it is being ridden on a wave. As a surfer rides down the face of a wave in high speed and performs a steep bottom turn maneuver at the bottom of the wave, the surfboard foam begins to bend into the turn and store potential energy. As the surfer comes out of the bottom turn and straightens the direction of the board toward the uppermost part of the breaking wave, also known as the “lip,” the surfboard springs back to its original shape, releases the potential energy to become kinetic energy and propels the surfer out of the turn. This burst of kinetic energy can be turned into an acceleration to help the surfer gain speed for the next maneuver. However, the balance between flexibility and rigidity of the surfboard must be maintained to prevent the surfboard from snapping during bending.
Surfboards are typically constructed of polyurethane foam, polystyrene foam, expanded polystyrene foam, or extruded polystyrene foam, which are subsequently laminated by fiberglass cloth, Kevlar or carbon fiber for additional strength. However, the foam and the laminating materials by themselves are relatively weak to withstand bending. Therefore, to maintain the structural integrity of the surfboard due to bending, a strip of wood known as a “stringer” is typically embedded in the middle of the surfboard foam extending from the tail to the nose. The stringer effectively provides a spine to the foam that increases the strength and rigidity of the surfboard. Commonly used wood for stringers are balsa wood, basswood, redwood, cedar and birch.
While the addition of the stringer to the foam increases the strength and rigidity of the surfboard, there are a number of problems associated with the stringer. First, a conventional stringer that is placed in the middle of the surfboard, or a “center stringer,” often results in a surfboard that is rigid along the center of the surfboard, but weak and flexible along the surfboard's curved perimeter edges, commonly known as the “rails.” This inconsistent rigidity throughout the surfboard is known as a torsion flex, which causes the board to be non-uniform in its flex, inconsistent in its plane, lose its drive and slow down while traveling on a wave.
To address the issue of torsion flex, a known technique in the art places the stringers on and along the rails of the surfboard instead of in the middle of the surfboard. This type of stringers is known as “parabolic stringers.” The theory behind the parabolic stringers is that by strengthening the rails, the foam can bend and spring back to its original shape quicker while the structural integrity of the foam is maintained and somewhat more uniform. However, employing parabolic stringers significantly increases the cost of labor in surfboard construction, as the blank foam must first be cut in a parabolic arc, and the wooden stringer must have a certain thickness, carefully hand bent and hand glued along the rails to follow the outline of the surfboard. Additionally, as the center stringer is typically used as a reference point of symmetry, shaping a surfboard with parabolic rails is difficult and time consuming.
An obvious issue related to the use of stringers in surfboard construction is the added material and labor costs, as some types of wood may be expensive and difficult to install into the blank foam. In addition, having the wooden stringer and glue in the foam increases the weight of the surfboard, which may affect the performance of the surfboard and consistency of the flex. Lastly, the wooden stringer reduces the shelf-life of the surfboard's responsiveness. After repeated compression and expansion due to the flex, a surfboard's traditional wooden stringer weakens, giving the surfboard a dead feeling.
Based on the foregoing, there is a need in the surfboard industry for a cost-effective surfboard that is lighter, stronger and more uniform in its flex characteristic without the use of traditional wooden stringers.